In recent years, so-called active matrix drive devices for driving liquid crystal display (LCD) panels, organic electroluminescence (EL) panels, and the like are known in the art. Such active matrix drive devices are semiconductor devices in which thin film transistors (TFTs) containing amorphous silicon (amorphous Si or a-Si) or polysilicon (p-Si) are formed on arbitrary substrates larger than silicon (Si) wafers, such as glass substrates and quartz substrates. Formation of higher performance Si devices has been studied in order to integrate peripheral drivers, or systems for which higher performance is required, such as memories, microprocessors, image processors, and timing controllers, on substrates.
In particular, polysilicon has received attention as a material that is used to integrate peripheral drivers having high mobility and operating at a high speed. However, polysilicon has localized levels in bandgaps due to crystalline imperfection, and has defects and localized levels near grain boundaries, causing problems such as reduced mobility, an increased S coefficient (subthreshold coefficient), and the like.
Moreover, in the case of forming TFTs on those substrates, such as glass substrates, whose processing accuracy is lower than that of Si wafers, miniaturization of devices is limited due to the relatively low processing accuracy. This makes it difficult to integrate systems requiring more sophisticated element portions, such as memories, microprocessors, image processors, and timing controllers, on the glass substrates.
As a solution to the above problems, Patent Document 1, for example, discloses a so-called transfer technique. Specifically, an element portion having a TFT is formed by using a silicon-on-insulator (SOI) substrate, which is formed by laminating an insulating layer and a semiconductor layer on a semiconductor substrate. Then, a delamination material is ion implanted into the semiconductor substrate to form a delamination layer. The element portion formed on the semiconductor substrate is transferred and bonded to another substrate, and a part of the semiconductor substrate is separated and removed along the delamination layer. This technique enables sophisticated element portions to be integrated on glass substrates or the like.